char * maximumTime(char * time){
    if (time[0] == '?') {
        time[0] = (time[1] <= '9' && time[1] >= '4') ? '1' : '2';
    }
    if (time[1] == '?') {
        time[1] = (time[0] == '2') ? '3' : '9';
    }
    if (time[3] == '?') {
        time[3] = '5';
    }
    if (time[4] == '?') {
        time[4] = '9';
    }
    return time;
}